THE WEIGHT EQUATION

What exactly is weight? Physics defines weight as a force measured in Newtons. Force is calculated by multiplying the mass of an object in kilograms by acceleration in meters per second squared (m/sec2). For our purposes on earth, acceleration is the effect of gravity, or 9.8 m/s2.
Weight or Force (Newtons) = mass (kg) x acceleration (m/sec2).
The mass of an object is more difficult to define but in general terms it is a fundamental measure of the “amount of matter” present in an object. In lay language, we tend to use weight and mass interchangeably but in physics they are distinctly different entities. If we lived on the moon or in outer space where gravitational forces are lower, then theoretically our weight would be lower (but our mass would remain constant). I guess one way to lose weight quickly would be to orbit the earth in space for a few days where gravity (acceleration) is low, but you would gain it back just as quickly when you return. Short of toying with gravitational acceleration, we have to be content with decreasing our body mass in order to lose “weight”.
In regular verbiage, we tend to say that we have “gained or lost weight” to mean that we have “gained or lost mass.” Therefore short of traveling through space, the fundamental question then becomes why do we gain or lose weight over time. The best way of looking at weight gain or loss is to relate it to the amount of energy taken in or put out of our body over time. One of the fundamental laws of physics is that energy is not destroyed; it just changes form over time. For example, when we turn on the gas oven to cook food, we are converting chemical energy (natural gas) mostly into heat energy (to cook), and light energy (the blue flame we see). Similarly, long term fluctuation in body weight is a reflection of the input of energy into the body versus the output of energy from the body over time. I’m not talking about the one or twp pounds you “gain or lose” over a few days. Rather concerned with the steady weight gain that occurs over months and years that sticks with you.
If energy input exceeds energy output over a period of time, weight gain occurs. If the reverse is true and energy output exceeds energy input, then weight loss occurs. If energy input and energy output are equal, then weight does not change. These relationships are summarized below.
ENERGY INPUT > ENERGY OUTPUT INCREASE IN WEIGHT
ENERGY INPUT< ENERGY OUTPUT DECREASE IN WEIGHT
ENERGY INPUT = ENERGY OUTPUT NO CHANGES IN WEIGHT
Sounds simple? It would be if energy input and energy output factors did not change over one’s lifetime. When we talk about energy input and energy output in terms of the body, we are essentially talking about calorie input and output. Human input and output of calories is highly dependent on the interaction of numerous societal, psychological, physiological and time dependent factors. But before we get further into the reason why weight gain occurs, we have to define some of the terms that we use frequently when we talk about weight gain or loss, diets, and energy.

CHILDREN AND OBESITY

There is real cause for concern with the current rise in obesity rates of children. According to recent statistics, the rate of childhood obesity has tripled for children and adolescents between the age of 6 and 19. In addition, it is estimated that a third of all children and adolescents in the United States are either already obese or at increased risk for becoming obese. Childhood obesity rates have increased substantially because of dietary and social factors. According to a 10-year study by the National Health and Nutrition Examination Survey (NHANES), overweight teens in the United States consume anywhere between 700-1000 calories more than the required daily allowance. This excessive intake of calories has resulted in an average weight gain of 58 extra pounds for teenagers. Even children and teens who are not overweight consumed 110-165 calories more than was required, leading to an average weight gain of 10 pounds of extra body weight over the study period. There have been numerous recommendations made as consequence of this study in order to try and reduce teen obesity rates. These recommendations include reducing consumption of sodas, which could save 150 calories per can. Increasing healthy food consumption in place of snacking as well as eating at home will tend to decrease overall calorie intake. In terms of activity levels, it has been recommended that teens spend less time watching television and more time exercising and playing. Regular physical education classes are advised in order to help kids burn the extra calories.
Childhood obesity has resulted in a significant increase in Type 2 diabetes in kids. We used to call Type 2 diabetes “adult onset diabetes” because it occurred mostly in adults. However, pediatricians are now finding that many of their diabetic kids are type 2 diabetics as a result of being overweight, rather than the typical type 1 (juvenile onset) diabetics that they used to encounter years ago. Part of the problem with overweight kids is poor choices in diet from an early age. The American Academy of Pediatrics recommends that kids between the ages of 6 months to 6 years drink less than 6 ounces of fruit juice daily. In addition, kids between the ages of 6 to 12 years should limit their intake of sweetened liquids such as sports drinks and sodas to less than 12 ounces a day.
The epidemic of childhood obesity is confounded by the fact that most parents don’t recognize that their own kids are overweight or obese. In a recent study on overweight or obese children between the ages of 6 to 11, 43% of parents thought that their kids were “about the right weight.” Another 37% of parents thought their child was “slightly overweight”, while only 13% recognized their child as being “very overweight.” For obese children in the 12-17 age group, 11% of parents thought their child was “about the right weight”, while 56% voted for “slightly overweight”, and 31% voted for “very overweight.” A small percentage of parents of these obese children thought that their kids were “slightly underweight!” These were kids who were all documented by clinical criteria to be obese! Now this result means that either parents have a distorted body image, or they don’t want to face the obvious fact that their children are overweight or obese.